Airbag devices that are inflated and deployed downward along vehicle-body side walls, like curtains (curtain airbag devices), to protect the heads of occupants in front seats and rear seats in an emergency stop of a vehicle, such as collision, have become common. Because such an airbag device is laterally longer than conventional airbag devices stored in, for example, steering wheels and instrument panels, the airbag is provided with a plurality of mounting tabs protruding from the airbag at an upper part thereof, corresponding to the lateral length thereof, via which the airbag is mounted to a vehicle-body side wall (for example, a roof-side rail).
Because these mounting tabs are subjected to a considerable tensile force when the airbag is inflated and deployed, one end of each mounting tab needs to be securely fixed to a vehicle-body side wall (for example, a roof-side rail) with a bolt etc., so that the mounting tabs of the airbag are not detached from mounting means (mounting brackets) when the airbag is inflated and deployed. Airbag devices having mounting structures for this purpose have already been proposed.
For example, there is known an airbag device in which a mounting tab provided so as to protrude from an airbag is sandwiched between two metal plates, and the airbag is mounted to a vehicle-body side wall in this state (PTL 1).
In this airbag device, the airbag is fixed by crimping the two metal plates together to integrate the metal plates and the mounting portion (the mounting tab), inserting a bolt into mounting holes provided in the mounting portion and the metal plate, and screwing the bolt into a fixing hole provided in an inner panel (a vehicle-body side wall) and a nut welded to the inner panel.
Furthermore, separately from the above airbag device, there is known an airbag device in which an edge (a mounting tab) of an airbag body is sandwiched between a bent metal plate, and this metal plate is mounted to a roof-side frame (a vehicle-body side wall) of a vehicle with a bolt (PTL 2).
However, because the airbag device disclosed in PTL 1 has a structure in which the mounting portion (the mounting tab) of the airbag is sandwiched between the pair of metal plates, and in this state, the bolt is inserted through the metal plates, the mounting portion, and the inner panel and screwed into the nut, thereby integrally fastening these components, the mounting portion sandwiched between the pair of metal plates serves as a cushion when the bolt is fastened, making it difficult to obtain a feeling of contact when the bolt is fastened. Hence, it is difficult to fasten the bolt with a predetermined torque. In addition, when a state in which the mounting portion is compressed between the pair of metal plates lasts for a long time, the torque of the bolt may decrease due to thermal expansion and deterioration of the mounting portion (the mounting tab).
Also in the airbag device disclosed in PTL 2, because a bent back claw is pushed toward the plate by the vehicle-body side wall and compresses the edge (the mounting tab), the edge serves as a cushion, making it difficult to obtain a feeling of contact of the bolt. Furthermore, similarly to the airbag device disclosed in PTL 1, a decrease in torque due to aging may occur.
Meanwhile, to overcome these problems, there has been proposed an airbag device having a mounting bracket that is configured to sandwich a mounting tab portion (a mounting tab) of an airbag between outer and inner plate portions but that prevents the mounting tab portion from serving as a cushion, thereby making it possible to obtain a feeling of contact when a bolt is fastened (PTL 3).
In this airbag, as shown in FIG. 5, a mounting bracket 134A is composed of inner and outer plate portions 136A and 135A, a peripheral edge portion of a mounting hole 136a in the inner plate portion 136A is provided so as to be substantially in flush with a vehicle-exterior-side surface of the outer plate portion 135A, and a mounting bolt 138, which is allowed to penetrate through an insertion hole 132a in a mounting tab portion 132 and a mounting hole 135a in the outer plate portion 135A and protrudes toward a vehicle exterior side, is screwed into a nut 102b attached to an inner panel 102.
Furthermore, in a mounting bracket 134B shown in FIG. 6, the inside diameter of a mounting hole 136a in an inner plate portion 136B is set substantially the same as the inside diameter of a mounting hole 135a in an outer plate portion 135B. A head 138a of a mounting bolt 138 is abutted against the periphery of the mounting hole 136a in the inner plate portion 136B, and a fastening shaft 138b of the mounting bolt 138 is fastened to a nut 102b on an inner panel (a vehicle-body side wall) 102, thereby directly joining the inner and outer plate portions 136B and 135B.
With the mounting brackets 134A and 134B of the airbag device in PTL 3, it seems that the mounting tab portion 132 does not serve as a cushion, a feeling of contact is obtained when the mounting bolt 138 is fastened, and a decrease in torque after fastening does not occur.
However, with this airbag device, when the mounting tab portion 132 of the airbag is fixed to the inner panel 102, the inner plate portion 136A or 136B and the outer plate portion 135A or 135B have to be separately fitted and positioned with respect to the mounting tab portion 132 from the front and back. Furthermore, to integrate the mounting tab portion 132 and the outer plate portions 135A and 135B and the inner plate portions 136A and 136B in advance, portions to be deformed are provided in the outer plate portions 135A and 135B and the inner plate portions 136A and 136B, and the portions to be deformed are crimped. However, if the portions to be deformed are just crimped, they may come off during conveyance etc. Furthermore, when the airbag is mounted to the inner panel, the mounting bolt needs to be inserted into the mounting tab portion 132 and the outer plate portions 135A and 135B and the inner plate portions 136A and 136B. Thus, mounting work inevitably becomes complex.
Under the circumstances, there is a demand for an airbag device in which mounting of an airbag to a vehicle body is easy, a feeling of contact can be obtained when mounting tabs of the airbag are fastened with bolts, as in the conventional airbag device, and furthermore, the mounting work can be easily performed.